Retention behavior of alkali, alkaline earth and transition metal cations in ion chromatography with an unmodified silica gel column

An unmodified silica gel (Develosil 30-5) column (150×4.6 mm I.D.) has been applied to the ion chromatographic separation of alkali, alkaline earth and transition metal cations. The retention behavior of the above cations on the bare substrate was investigated using a number of weak inorganic and organic acid eluents. During this investigation, several separations were achieved and the most suitable eluent conditions were identified. It was concluded that: (a) 1.5 mM HNO₃-0.5mM pyridine-2,6-dicar☐ylic acid eluent was the most effective for the simultaneous separation of common alkali and alkaline earth metal cations, (b) 1.5 mM oxalic acid eluent resulted in the best separation of alkali, alkaline earth, and transition metal cations, (c) 0.5 mM CuSO₄ eluent could be used for the separation of alkali metal cations alone and (d) 0.5 mM ethylenediamine-oxalic acid eluent at pH 5.5 resulted in themost efficient separation of both alkaline earth and transition metal cations.